Sterling 30RA010-055 manual B — Configuring Return Temperature Reset

Table 26A — Configuring Outdoor Air and Space Temperature Reset

MODE	KEYPAD	SUB-	KEYPAD		DISPLAY		ITEM
				ITEM	Outdoor			COMMENT
(RED LED)	ENTRY	MODE	ENTRY			Space	EXPANSION
					Air
	ENTER	DISP
		UNIT
		OPT1
		OPT2
CONFIGURATION			ENTER				COOLING RESET	2 = Outdoor-Air Temperature
		RSET		CRST	2	4		4 = Space Temperature
							TYPE	(Connect to TB5-5,6)
				RM.NO*	85 °F	72 °F	REMOTE - NO	Default: 125.0 F (51.7 C)
							RESET TEMP	Range: 0° to125 F
				RM.F	55 °F	68 °F	REMOTE - FULL	Default: 0.0° F (-17.7 C)
							RESET TEMP	Range: 0° to 125 F
							REMOTE - DEGREES	Default: 0° F (0° C)
				RM.DG	15 °F	6 °F		Range: –30 to 30 F
							RESET
								(–34.4 to -1.1 °C)

*4 items skipped in this example.

Table 26B — Configuring Return Temperature Reset

MODE	KEYPAD	SUB-MODE	KEYPAD	ITEM	DISPLAY	ITEM		COMMENT
(RED LED)	ENTRY		ENTRY			EXPANSION
	ENTER	DISP	ENTER	TEST	ON/OFF	TEST DISPLAY LEDs
		UNIT	ENTER	TYPE	X	UNIT TYPE
		OPT1	ENTER	FLUD	X	COOLER FLUID
		OPT2	ENTER	CTRL	X	CONTROL METHOD
			ENTER				0	= No Reset
							1	= 4 to 20 mA Input (EMM required)
CONFIGURATION		RSET		CRST	X	COOLING RESET TYPE	2	(Connect to EMM TB6-2,3)
								= Outdoor-Air Temperature
							3	= Return Fluid
							4	= Space Temperature
								(Connect to TB5-5,6)
				RT.NO*	XXX.X ∆F	RETURN FLUID - NO	Default: 10.0 ∆F (5.6 ∆C)
						RESET TEMP	Range: 0° to125 F COOLER ∆T
				RT.F	XXX.X ∆F	RETURN FLUID - FULL	Default: 0 ∆F (–17.8 ∆C)
						RESET TEMP	Range: 0° to 125 F COOLER ∆T
				RT.DG	XX.X ∆F	RETURN - DEGREES	Default: 0 ∆F (0 ∆C)
						RESET	Range: –30 to 30°F (–16.7 to 16.7 C)

*4 items skipped in this example.

Temperature Reset — The control system is capable of handling leaving-fluid temperature reset based on return cooler fluid temperature. Because the change in temperature through the cooler is a measure of the building load, the return tempera- ture reset is in effect an average building load reset method. The control system is also capable of temperature reset based on outdoor-air temperature (OAT), space temperature (SPT), or from an externally powered 4 to 20 mA signal. Accessory sen- sors must be used for SPT reset (33ZCT55SPT). The Energy Management Module (EMM) must be used for temperature reset using a 4 to 20 mA signal. See Tables 25A and 25B.

IMPORTANT: Care should be taken when interfacing with other control systems due to possible power supply differ- ences: full wave bridge versus half wave rectification. Con- nection of control devices with different power supplies may result in permanent damage. ComfortLink™ controls incorporate power supplies with half wave rectification. A signal isolation device should be utilized if the signal gen- erator incorporates a full wave bridge rectifier.

To use Outdoor Air or Space Temperature reset, four vari- ables must be configured. In the Configuration mode under the sub-mode RSET, items CRST, RM.NO, RM.F and RT.DG must be properly set. See Table 26A — Configuring Outdoor Air and Space Temperature Reset. The outdoor air reset exam- ple provides 0° F (0° C) chilled water set point reset at 85.0 F (29.4 C) outdoor-air temperature and 15.0 F (8.3 C) reset at

55.0F (12.8 C) outdoor-air temperature. The space tempera- ture reset example provides 0° F (0° C) chilled water set point reset at 72.0 F (22.2 C) space temperature and 6.0 F (3.3 C) reset at 68.0 F (20.0 C) space temperature. The variable CRST should be configured for the type of reset desired. The variable RM.NO should be set to the temperature that no reset should occur. The variable RM.F should be set to the temperature that maximum reset is to occur. The variable RM.DG should be set to the maximum amount of reset desired.

To use Return reset, four variables must be configured. In the Configuration mode under the sub-mode RSET, items CRST, RT.NO, RT.F and RT.DG must be properly set. See Table 26B — Configuring Return Temperature Reset. This ex- ample provides 5.0 F (2.8 C) chilled water set point reset at

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